This invention relates to a novel head and bristle configuration for the trim pattern of a toothbrush. The bristles are arranged in tufts and the bristle ends of each tuft are trimmed to produce a concave shape. Such a concavity resembles the concavity of a rubber prophy cup used by dentists when polishing tooth surfaces.
While a rubber prophy brush is widely known, it is not in general known to employ bristle trim patterns that resemble the shape of rubber prophy cups. Instead, virtually all the known toothbrushes and designs had the following trim patterns covering the entire bristle field: flat, bi-level, multi-level, curved, slanted, saw-tooth, wavy, etc.
Toothbrushes having bristles arranged in a single "mat" covering substantially the entire area of the bristle face are known, e.g., in U.S. Pat. No. 4,646,381, which also discloses a toothbrush having a combination of circular sectioned tufts, oval sectioned and rectangular sectioned tufts located within a middle are of a larger mat of individual bristles covering a substantial area of the bristle face. U.S. Pat. No. 4,268,933 discloses a toothbrush having bristles arranged in large tufts of a rectangular shape, having their long dimension aligned substantially across the width of the toothbrush head. U.S. Pat. No. 2,209,173 discloses a toothbrush having elongated rectangular tufts of bristles with their long dimension aligned substantially parallel to the toothbrush axis, alternating with rectangular tufts which tilt together, the bristles in the tufts being flattened to form a sharp-edged tuft.
Bristle tufts having a substantially circular cross section have substantially the same stiffness to bending perpendicular to the longitudinal axis of the bristles in the tuft ("the tuft axis") whether this direction is parallel to the toothbrush axis or perpendicular to the toothbrush axis, i.e., across the width of the toothbrush. This can have the disadvantage that the tufts have substantially the same stiffness when the head is being moved generally in the direction of the toothbrush axis across the teeth parallel to the gumline, as when the head is being moved in a direction generally perpendicular to the toothbrush axis, up and down the teeth, crossing the gumline. It is desirable that a toothbrush is softer, i.e., has less stiffness to bend when brushing across the gumline, to prevent injury to the gumline.
U.S. Pat. No. 2,317,485, to Rider, issued Apr. 27, 1943, relates to a toothbrush with improved cleaning ability due to the shape and nature of the bristles. The Rider invention stems from the observation that circular cross-sectional bristles do not pack into tuft holes well and that other regular geometric shapes, e.g., triangles, squares, pentagons, hexagons, heptagons, and octagons, allow one to pack more bristles into a given tuft hole. Also, U.S. Pat. No. 2,876,477 to Stewart, issued Mar. 10, 1959, relates to another toothbrush which utilizes polygons of regular cross-sections, e.g., squares, pentagons, hexagons, heptagons, octagons, nonagons, etc. Contrary to Rider, Stewart seeks to maximize interstitial spacing by providing these polygons with a concave contour on each side. Still further, U.S. Pat. No. 3,032,230 to Poppelman, issued Feb. 7, 1967, relates to a toothbrush wherein the bristles, head and handle are molded into a single unit. Poppelman indicates that the preferred bristle cross-section should be of a polygon with at least two acute angles, e.g., triangle, rhombus, and a four-pointed star pattern.
Conventional, perpendicularly oriented bristle tufts tend to act as a series of columns and thus support suspended bristles as they pass over embrasures. This minimized overall compression strength afforded by this angle configuration allows individual tufts of bristles to penetrate embrasures, sub-gingival and interproximal spaces without being inhibited from doing so by surrounding bristle tufts.
Angled tufts move in the direction of their angle. As downward and horizontal force is applied to the brush head, tufts of bristle skid across tooth surfaces generally in the direction dictated by the angle of the tuft hole in which the bristles are anchored to the brush head rather than simply curling back in the opposite direction in which they are pushed. The preferred construction is to integrate multi-directional motion of bristles during unidirectional actuation of the brush.
When forced into the direction of their angle, bristles will spring out of crevasses as stresses are exceeded to contain them in place. This dynamic action will tend to fling plaque out of interproximal spaces. Conventional devices tend to pack plaque into spaces as the bristle tufts sweep over embrasures.
The weak flexure strength of spaced individual bristle tufts allows for the reduction of bristle height without causing the sensation of increased bristle stiffness. Conventional brushes trimmed to a shorter height are perceptibly stiffer and tend to cause trauma to the mucosa. Minimized bristle height allows for greater clearance (and thus enhance reach to the rear molars) between the buccal surfaces of the teeth and the mucosal lining.
Angled tufts of bristle will assume varying heights as they are deformed, yet will be uniform in height when not in use. Angled bristles will project above the tips of straight bristles as the former are forced into a perpendicular orientation during use. This effect, caused by the greater length of the hypotenuse of a triangle, allows for the angled tufts to reach deeply into the interproximal and gingival marginal areas as perpendicular orientation is assumed.
There are a number of known toothbrush constructions, however, none appear to exhibit a tuft arrangement which performs several tooth and gumline cleaning functions regardless of the style or technique employed for brushing. While a number of toothbrush manufacturers print specific brushing techniques on their brush containers, if a purchaser does not pay attention to them, or forgets them, then less than optimum teeth cleaning results.
EP-A-022 1000 discloses a toothbrush for a special use namely for teeth controlled by orthodontic braces. It has a line of central bristles perpendicular to the head and bristles located on either side and near the center and tilted outwardly and bristles located near the edges of the head and tilted inwardly. The bristles are not arranged in rows transverse to the head. The relationship of the tilted bristles to the perpendicular bristles appears to be random.
U.S. Pat. No. 2,168,984 discloses a single central perpendicular bristle 6, then a pair of perpendicular bristles 4 along the head towards the handle, then a pair of inwardly inclined bristles 3, then four bristles 2,5,5,2, the outer two 2,2 being perpendicular and the inner bristles 5,5 being inclined outwardly. The rows (4,4), 3,3) and (2,5,5,2) then repeat and the head ends with a row (4,4).
Swiss Patent CH-A-324623 has two bristles inclined to the same side at the tip and then alternating rows of three bristles, all the bristles in one row being inclined to the same side and the inclination alternating from row to row.
Brushes may be manufactured by any one of several technologies currently available. The body itself, as noted above, may be injection molded, in a single or multistep process. While certain of the bristles may be attached by staples as is conventional, the bristle bars, scoops and other densely packed bristles generally must be attached using newer staple-free technology such as fusion or injection molding, with the latter often being employed. Fusion technology, whereby the brush body is preformed then softened and the bristle tufts are melted and fused to the softened brush body is useful.
Injection molding is carried out on machinery which is known in the following patents, each of which is expressly incorporated herein by reference: U.S. Pat. No. 4,430,039, issued Feb. 7, 1984; U.S. Pat. No. 4,580,845, issued Apr. 8, 1986; U.S. Pat. No. 5,143,425, issued Sep. 1, 1992; and U.S. Pat. No. 5,390,984, issued Feb. 21, 1995.
Other useful techniques for attaching bristles to a body, such as thermoforming, fusion, welding, and the like are illustrated in the following patents, which are expressly incorporated herein by reference: U.S. Pat. No. 4,109,965, issued Aug. 29, 1978; U.S. Pat. No. 4,619,485 issued Oct. 28, 1986; U.S. Pat. No. 4,637,660 issued Jan. 20, 1987; U.S. Pat. No. 4,646,381 issued Mar. 3, 1987; U.S. Pat. No. 4,892,698 issued Jan. 9, 1990; U.S. Pat. No. 5,045,267 issued Sep. 3, 1991; U.S. Pat. No. 4,988,146 issued Jan. 29, 1991; and U.S. Pat. No. 5,224,763 issued Jul. 6, 1993.
Prior to the availability of newer technology, it was customary to install bristles in toothbrush heads by the use of small staples. Several bristles (later to form a tuft), only slightly longer than twice the desired bristle length, were essentially folded about their mid lengths. The bight of the folded bristles is inserted into a respective hole in the head. Then a small staple is driven into the head substrate such that its legs or prongs entered the substrate and its bight portion bore against the bight of the folded bristles. Alternatively, the insertion of both the folded bristles and the staple was carried out at the same time. The holes in the toothbrush head were formed either by drilling or by molding.
By virtue of the newer technology the manufacturer of toothbrushes can insert single bristles into a toothbrush head without the need to first bend a plurality of them to thereby form a central bight portion or region against which a part of a staple abuts to anchor the bristles into place in the head. Thus each bristle may be individually customized to a specific and desired length prior to its insertion into the head. Further, instead of each tuft receiving hole requiring a diameter large enough to accommodate a bundle or group of folded bristles, the diameter need be only as large as the diameter of a single tuft. In turn this new manner of bristle attachment permits increased head strength due to the increased volume of substrate material between the several tufts of the head.
Staple-free attachment results in no holes in the brush body, where water can collect and bacteria grow. Most preferred is supplying the bristles to an injection mold, and injection molding the brush body around the bristles for a tight fit. Rubber grips may be injection molded over the body.